JPS5922228B2 - Exposure method for color electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure method for color electrophotography.

In the generally known color electrophotographic method, for example, color filters of three primary colors such as red, blue, and green are sequentially inserted into the optical path, and the photoreceptor is exposed to light that passes through the color filters. However, the light transmittance differs depending on the color of the color filter, and the light emitted from the light source that illuminates the document often has a wavelength distribution specific to the type of light source.

FIG. 1 is a diagram showing the spectral transmittance of a Wratten filter commonly used in color electrophotographic devices.

In the figure, TB (λ) is related to the blue filter, TG (
λ) is related to the green filter, and TB (χ is related to the red filter. FIG. 2 shows the wavelength distribution of the intensity of light emitted by a halogen lamp, which is a common light source for electrophotographic devices.

Then, .

Ofol(λ)TB(λ)dλ (1) °o , lol(λ)TG(force d(λ) (2).

O,lol(blade TR(λ)dλ (3) represent the intensity of light from the halogen lamp transmitted through the blue, green, and red Wratten filters, respectively.

The ratio of these strengths is 1.1 (blade TB (λ) dλ:, 1.1 (support) TG (■
I ■) dλ:, 1ol(λ) TR(λ) dλ=1: 4
: 20=0.05: 0.2: 1(4).

The rate at which a photoreceptor, whose spectral sensitivity characteristics are uniform for wavelengths in the visible region, is exposed to light is proportional to the amount of light, or intensity, of the exposed light, so the photoreceptor is exposed to blue, green, and red light. Conventionally, in order to equalize the exposure amount for each color, in the case of the full exposure method, the lighting time of the light source, the aperture of the lens, etc. must be adjusted to make the exposure amount equal for each color. There is a drawback that the amount of light must be corrected by changing each color filter or, in the case of the slit exposure method, by changing the scanning time of the document for each color filter.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure method for color electrophotography that eliminates the above-mentioned drawbacks and allows proper exposure for any color filter with the same exposure time using a simple mechanism. be.

The present invention will be described below with reference to the drawings.

FIG. 3 shows only the essential parts of an exposure device of a color electrophotographic apparatus for carrying out the present invention. That is, the exposure device includes a transparent document placing table 1 that places document 0 during exposure and moves in the direction of the arrow, and a transparent document placing table 1 that rotates in the direction of the arrow at a circumferential speed equal to the moving speed of this document placing table 1. Photosensitive drum 2
It consists of an exposure optical system 3, a halogen lamp 4 as a light source, and a light amount control member 5, which are arranged at a fixed position between the two. As shown in FIG. 4, the exposure optical system 3 consists of a large number of thin rod-shaped photoconductors (trade name) having light focusing properties, which are arranged in parallel to each other and bundled in the densest manner. At both ends, the collective surfaces of the end faces of the individual light guides 31 form corresponding elongated rectangular faces, and a large number of light guides aligned in this way are held in a resin holder 3.
It is fixed at a.

Direction A shown in FIG. 4 is the width direction of the elongated rectangular surface. The length direction of this exposure optical system 3 is arranged parallel to the width direction of the original table 1. The distance between the end surface of the exposure optical system 3 on the side of the document 0 and the document 0 is the distance between the end surface of the exposure optical system 3 on the side of the photoreceptor drum 2 and the closest part of the photoreceptor drum 2 to the exposure optical system 3. is equal to the distance between the planes of The self-container that is the light guide 31 is a thin bar-shaped glass with a circular cross section, and its refractive index changes symmetrically with respect to its central axis in the radial direction as expressed by the following equation.

Here, r is the distance from the central axis.

Then, the light incident on the self-lock from the end face moves toward the central axis with a period of 2π/! Proceed by drawing the sine curve A.

Therefore, the individual light guides 31 are each independent. Work carefully to make the light guide an appropriate length, for example,
If arranged as shown in FIG. 3, an erect image of the original 0 at the same size can be obtained on the surface of the photosensitive drum 2. Now, since the light guides 31 are bundled most densely, the rows of light guides aligned in the length direction of the exposure optical system 3 are arranged so that in adjacent rows, the positions of the light guides are separated by the radius of the light guides. Shifted along the length of the column. Below, for the sake of simplicity, two adjacent
The rows are set as one array, and the width direction of the exposure optical system 3, that is, FIG.
It is assumed that 10 arrays, ie, 20 rows of light guides are lined up in the direction. Further, if the width of one array is d, then in the exposure optical system 3, the area of the elongated rectangle formed by the collective surface of the end faces of the individual light guides 31 is 10 dX1. However, here l is the length of the above rectangle. As shown in FIG. 5, the light amount control member 5 has blue lattice filters 5B1, green lattice filters 5G1, and red lattice filters 5R1 in some places on the light shielding member 5e which does not allow light to pass through.
A neutral density filter 5d is installed, and a neutral density filter 5a is installed in the green filter 5G, and a red filter 5R is installed in the green filter 5G.
A neutral density filter 5c is superimposed on the filter.

In this way, by using the neutral density filter 1 together with the ratten filters 5G and 5R, the degree of freedom in determining the width of these ratten filters 1 can be increased. That is, for example, when determining the appropriate width of only one ratten filter, this ratten filter is used.
If the width of the filter 1 becomes too narrow, it is possible to increase the width of the ratten filter 1 by using a neutral density filter 1 in combination. FIG. 5 is a view of the light quantity control cape member 5 viewed from the width direction, and the length of the light quantity control member 5 in the width direction is approximately equal to the length Z of the exposure optical system 3. The width of the blue filter 5B, that is, the length in the direction perpendicular to the width direction of the light amount control member 5 is 10
The width of the green filter 5G is approximately 4d1, the width of the red filter 5R is approximately 2d, and the width of the neutral density filter 5d is approximately 2d. Therefore, the area of these filters is approximately 10d1 for the blue filter 5B, 4d for the green filter 5G.
The area of the d11 red filter 5R and the neutral density filter 5d is 2d1. Of course, the area of the neutral density filter 5a is 4d.
11 The area of the neutral density filter 5c is 2d1. The neutral density filter is a filter that absorbs light in the visible region with a uniform absorption rate regardless of wavelength. The transmittance of the neutral density filter 5a is 62.5%, the transmittance of the neutral density filter 5c is 25%,
The transmittance of the neutral density filter 5d is selected to be 20%. The light amount control member 5 is movable in a direction parallel to the moving direction of the document mounting table 1. Now, the exposure of the photosensitive drum 2 by the exposure device is performed as follows.

That is, the halogen lamp 4 as a light source is turned on, the rotating drum 2 rotates in the direction of the arrow, and its surface is uniformly charged. Next, the document mounting table 1 starts moving in the direction of the arrow.
The surface of document 0 is scanned, but at that time, in the optical path,
A blue filter 5B is inserted. Then, manuscript 0
The amount of light of the blue component that passes through the exposure optical system 3 and passes through the blue filter 5B among the reflected light from the exposure optical system 3 is based on the amount of light transmitted when the blue filter 5B is replaced with a red filter 1 having the same area. Therefore, the surface of the photoreceptor drum 2 is exposed to blue light with an amount of light of 1/20 per unit time, and the blue color of original 0 is exposed on the surface of the photosensitive drum 2. An electrostatic latent image corresponding to an image of a color complementary to blue is formed, and as the photoreceptor drum 2 further rotates, the electrostatic latent image is transferred to a toner of a color complementary to blue. The visible image is transferred onto the recording sheet, or the electrostatic latent image is transferred onto the recording sheet and then converted into a visible image on the recording sheet. During this time, the light amount control leg member 5 moves in the direction of the arrow in FIG. 3, and the green filter 5G is inserted into the optical path.
The above process is repeated, and the surface of the photosensitive drum 2 is exposed to the light that has passed through the green filter 5G.
At this time as well, the moving speed of the document holder 1 is the same as that during color separation by the blue filter 5B. However, in this case, since the area of the green filter 5G is 4d1, 3/5 of the light transmitted through the exposure optical system 3 is blocked by the light blocking member 5e. That is, only the four arrays of light guides of the exposure optical system 3 are effectively used. 2 of the light passing through the exposure optical system 3
Another 62.5% of /5 is neutral density.
It passes through the filter 5a and further passes through the green filter 5G.
The amount of light transmitted through the neutral density filter 15a is 20% of the reference red component light amount 1 contained in the light transmitted through the neutral density filter 15a, so the surface of the photoreceptor drum 2 is , the light amount is 1/20 of the standard red component light amount per unit time. The same exposure process is repeated for the red filter 5R1 and the neutral density filter 5d, but in each case, the surface of the photoreceptor drum 2 has a light intensity of 1 per unit time of the reference red component. te1
It will be exposed with a light intensity of /20. Therefore, no matter which color filter is used, the time for scanning the document may be constant, and there is no need to change the amount of light emitted by the light source. As described above, according to the present invention, since the mechanism is simple, the apparatus can be simplified, and it is possible to provide an exposure method for color electrophotography that can properly expose each color filter with the same exposure time, which is extremely convenient.

[Brief explanation of drawings]

Figure 1 shows an example of the spectral transmittance of blue, green, and red Wratten filters, and Figure 2 shows an example of the wavelength distribution of the intensity of light emitted by a halogen lamp. FIG. 3 is a front view showing only the main parts of an example of an exposure device of a color electrophotographic apparatus for carrying out the present invention;
FIG. 4 is a partial plan view showing how the light guides are arranged in the exposure optical system shown as 3 in FIG. 3, and FIG. FIG. 0...Original, 1...Original mounting table, 2.
...Photosensitive drum, 3...Exposure optical system,
4...Halogen lamp, 5...Light amount control member, 5B...Blue filter, 5G...
. . . Green filter 1, 5R . . . Red filter 1, 5a, 5c, 5d . . . Neutral density filter 1.

Claims (1)

[Claims] 1. The light reflected from the document illuminated by the light from the light source is collected by bundling a large number of thin rod-shaped light guides with light-focusing properties to a certain length, aligning them parallel to each other, and connecting them at both ends. , an exposure optical system formed such that the collective surfaces of the end surfaces of the individual photoconductors form mutually corresponding elongated rectangular surfaces, the light is guided onto the photoreceptor to form an image corresponding to the original; In the color electrophotographic exposure method, the process is repeated by sequentially inserting multiple color filters of different colors into the optical path, depending on the light transmittance of each color filter and the wavelength distribution of light emitted by the light source. For each exposure process, the elongated rectangular surface of the exposure optical system is partially blocked in the width direction, and the area through which light passes through the exposure optical system is changed, or the area is changed and a neutral beam is placed in the optical path. A color electrophotographic exposure method characterized by inserting a density filter so that the same amount of light is exposed to a photoreceptor within the same exposure time in any exposure process.